In the following text, the following meanings are used, if not otherwise stated:
ACN acetonitrile;
ClSI bis(chlorosulfonyl)-imide, that is compound of formula (2);
CSI chlorosulfonyl isocyanate, that is compound of formula (3);
CSOS, CSA chlorosulfonic acid;DCB dichlorobenzene, if not otherwise stated it is 1,2-dichlorobenzene;DCE dichloroethane, if not otherwise stated it is 1,2-dichloroethane;DCM dichloromethane;DFACl difluoro acetic acid chloride;DFAF difluoro acetic acid fluoride;halogen F, Cl, Br or L preferably F, Cl or Br, more preferably F or Cl.HFSI bis(fluorosulfonyl)-imide, that is compound of formula (1);
LiFSI Lithium bis(fluorosulfonyl)-imide, that is compound of formula (4);
TEA triethylamine;TFACl trifluoro acetic acid chloride;TFAF trifluoro acetic acid fluoride;VN valeronitrile;wt %, % by weight percent by weight.
HFSI is an intermediate used for the production of electrolytes in electrochemical devices such as in lithium ion batteries in form of its lithium salt LiFSI.
WO 2009/123328 A1 discloses a method for preparation of metal salts of symmetrical and asymmetrical fluorosulfonylimide in a solvent by a reaction of a respective symmetrical or asymmetrical chlorosulfonylimide with a fluoride compound containing at least one element selected from the group consisting of elements of Group 11 to Group 15 and Period 4 to Period 6 (excluding arsenic and antimony), these metal salts are then converted in a second step to salts of various amines and symmetrical and asymmetrical fluorosulfonylimide in a cation exchange reaction.
US 2015/0246812 A1 discloses a method for the preparation of symmetrical and asymmetrical flourosulfonylimides from symmetrical and asymmetrical chlorosulfonylimides, wherein the reaction is done in an organic solvent.
WO 2015/012897 A1 discloses a method for producing FSI from ClSI using HF, wherein the HCl that is produced by the reaction is selectively removed during the reaction to produce HFSI in at least 80% yield. The reaction takes place at ambient (e.g. atmospheric) pressure. Reaction times are much longer than 3 hours. Both requirements, the rather long reaction times and the requirement for separating HCl from the reaction mixture during the reaction, require a special continuous stirred-tank reactor (“CSTR”) set-up with a device for the required separation of HCl during the reaction when carrying out the reaction in a continuous way. To do the reaction in a simple continuously working tube shaped reactor creates problems.
Also disclosed is the exchange of Br and I instead of Cl against F, that is the conversion of hydrogen bis(halosulfonyl)imide (HXSI) with hydrogen fluoride for producing hydrogen bis(fluorosulfonyl)imide (HFSI), where each X is independently a nonfluoro-halide, such as Cl, Br, or I.
WO 2015/004220 A1 discloses a method for the preparation of imidodisulfuryl compounds in a continuous reaction at elevated temperatures.
U.S. Pat. No. 7,919,629 B2 discloses in Example 10 the reaction of distilled ClSI with HF and reports i.a. 55% yield for the example with 2 h at 130° C.
There was a need for a method for preparation of HFSI that does not require mandatorily a solvent, that does not require mandatorily metal salts, and that has few steps, that produces HFSI in high yields and in that can done both batch wise and in a continuous manner in a continuous reactor, and also and a continuous tube shape reactor.
The method should not require the separation of HCl during the reaction for enhancement of the yield, as it is disclosed in WO 2015/012897 A1 and should allow to carry out the reaction in relatively short reaction times.
Unexpectedly a method for preparation of HFSI was found starting from ClSI, that does not require a solvent, that does not require metal salts, that has few steps, that produces HFSI in high yields in spite of the poor solubility and miscibility of HF in ClSI and vice versa, and that can be done both batch wise or in a continuous manner and also in a continuous tube shape reactor, and that is distinguished by short reaction times.
Unexpectedly, the method does not require the separation of HCl during the reaction, which is formed by the reaction, and still provides HFSI in good yields. This was unexpected in view of the disclosure of WO 2015/012897 A1. Furthermore it was unexpected that the use of a mixture comprising ClSI, CSI and chlorosulfonic acid in the reaction with HF provides for significantly higher yield than the use of ClSI alone as disclosed in U.S. Pat. No. 7,919,629 B2. This is exemplified herein with Comparative Example (i) versus Example 7.
The reaction can be done with relatively short reaction times compared to the disclosure in the prior art, which allows to do the reaction not only batch wise, but also in continuous manner, also in a continuous tube shape reactor.